The present invention is described in the context of an optical disk recorder. Before an optical disk can be used, either written to or read from, the disk definition tracks must be first read from the disk so that the disk's format and locations of defects are known before operations ensue. The definition tracks store sets of tables. Each set of tables is copied four times. There are two copies at the disk inner diameter and two copies at the disk outer diameter. Each set of tables has three tables or ordered lists. A first table is a disk definition structure (DDS) which is the directory of the data stored on the disk as well as locations of other system information. A primary defect list (PDL) identifies those sectors on the disk that were defective at the disk certification. The third table is the secondary defect list (SDL) which lists the sectors which became defective after certification. In the illustrated embodiment of this application, the DDS and the PDL are respectively stored in separate sectors in each copy.
It is extremely important to the successful operation of the data storage system employing such an optical disk that all four copies or sets have congruence. If any one copy is incomplete, then errors can occur during operations. The tables on each disk can be constructed in accordance with the proposed American Institute (ANSI) proposed standard having internal identification number X3B11/89-120. This proposed standard was sent for distribution for public comment under number X.192-199X. This proposed standard relates to 3.5 inch magnetooptic disk data storage systems.
A prior method of reading the control data structures described above is described in the proposed ANSI standard. Each set of tables is read sequentially. If a full set of tables can be read, then no attempt is made to read another set of tables, i.e., the first successfully read set of tables is used in disk storage operations. There was no ability to combine tables if a defective sector exists in anyone of the sets of tables. A defect in each of the sets of tables could make the disk unaddressable because the contents of these tables would be unknown for at least one portion of the disk. It is desired to provide for maintaining the integrity of the four copies of the control data structures and for ensuring congruence among the copies.